China is sending an envoy to Sudan and South Sudan to help resolve a dispute over oil exports, of which China is a major customer.

The foreign ministry in Beijing said Monday that China's special representative on African affairs, Liu Guijin, will visit the two countries in the coming days.

Sudan blocked the landlocked south from exporting oil last week, citing South Sudan's failure to pay certain transit fees.

Sudan later said it would take about a quarter of southern oil production in lieu of payment. South Sudanese officials described the plan as extortion and theft.

China depends on the two Sudans for about five percent of its oil.

The south took over about three-quarters of Sudanese oil production when it split from the north in July. The new country still depends on northern pipelines and port facilities to send its oil abroad.

Relations between Sudan and South Sudan have been tense, with the sides unable to agree on several major issues, including borders and oil revenue sharing.